Ultrasonic phased array instruments provide a significant advantage for many applications because they display a cross section of the region being inspected, thereby faciltating the visualization of a defect, its feature, location and size, typically sought by ultrasonic inspection. Another significant advantage of ultrasonic phased array instruments is that they provide much higher productivity in comparison to single-element probe systems.
A typical ultrasonic phased array instrument uses a probe comprised of an array of small sensor elements, each of which can be pulsed individually in accordance with focal laws, to steer and focus excitation signals, and received signals.
For industrial phased array and single element ultrasonic NDT/NDI applications, wedges are used to refract (Snell's Law) the ultrasonic wave from an ultrasonic transducer (probe element) into the material under test. When creating a two dimensional image or individual A-scans, parameters such as wedge or incident angle, wedge velocity, and height of the first element must be known. These wedge parameters are used to delay A-scans to compensate electronically for the time the acoustic wave travels in the wedge. This compensation provides for more readily interpreted A-scans. Along with the test object material properties, these wedge parameters are also used to determine the refracted angle of the acoustic wave in the test object material as calculated using Snell's Law.
In existing practice, the basic wedge parameters are manually provided to ultrasonic NDT/NDI instruments. This information is usually provided by the wedge manufacturer in the form of a specification sheet or an engraving on the wedge. Additionally, modern ultrasonic acquisition devices of NDT/NDI typically have a database of wedges from which the wedges can be chosen. The wedge part number, which is often engraved on the wedges, is typically required in order to choose an appropriate wedge data from the database.
Manually providing input regarding wedge parameters into an ultrasonic NDT/NDI system is prone to error for many reasons. For new wedges, variation in fabrication tolerances can, to some degree, cause variation in mechanical parameters. Acoustic velocity also varies between different batches of wedge material. Also, wedge specification sheets are often lost or missing. In addition, there can be more information associated with a given wedge than can be engraved on a small wedge, and the engravings can fade with wedge usage. Also worth noting is that, with usage, wedges can become worn thereby the angle of a wedge and height of the first element can be changed. Also the parameters are typically reported as designed and not as manufactured. The method does not account for manufacturing tolerances in the wedge, the probe and the mounting of the probe onto the wedge, all of which lead to inspection errors. In addition, when giving recommended wedge parameters, manufacturers do not take into consideration the variations in wedge working temperature which can affect the velocity of sound in the wedge and therefore the refraction angle produced in the material under inspection is not as accurate.
It is commonly recognized that existing wedge identification methods not only are cumbersome and costly, but also lack accuracy which may be significant when critical information is missed during an ultrasonic inspection.
The present disclosure aims to automatically detect wedges for ultrasonic NDT/NDI devices and describes methods and systems to achieve that objective. Some examples are to store wedge identification information in the form of RFID, coded electronics, printed bar coded and EPROM, which are affixed inside or on the surfaces of the wedges. While these potential methods could deliver the basic wedge information to the instrument, they do not account for the factors caused by wedge wear, variations in the velocity due to temperature changes and variations in material due to manufacturing process. As a result, the accuracy of the information is compromised. Furthermore, these methods need extra material and operational steps to implement and therefore are not economical.
On the other hand, it is an existing practice in many applications that after the probe and wedge parameters are provided to the instrument, time-of-flight wedge calibrations are performed. Time-of-flight calibration of wedges is used to fine tune the acoustic time-of-flight within the wedge which may vary somewhat with respect to the manufacturer recommended parameters provided for each wedge and also with respect to wear. However, this practice does not solve the issue of identifying the wedge at the beginning of each phased array operation and the calibration can only be done periodically. In addition, wedges still need to be identified before any calibration process.
There is therefore a long felt, but unmet, need to provide an easier to use, less costly and more versatile approach to enable automatic wedge identification for ultrasonic phased array systems.